Research hints at a sea of ammonia under Pluto's icy surface

NASA’s New Horizons spacecraft captured this high-resolution enhanced color view of Pluto on July 14, 2015.

NASA/JHUAPL/SwRI

Data from NASA's New Horizons spacecraft suggest that a syrupy ocean filled with ammonia could dwell beneath Pluto's icy shell.

There is no direct evidence for an ocean on Pluto, but scientists argue it's very likely, given that a subsurface ocean would explain the planet's particular rotation and tectonics. In a recent paper published in the journal Nature, researchers mused that an ocean at extremely low temperatures could be maintained if it contained ammonia. Ammonia has also been detected by the New Horizons probe on two of Pluto's moons.

"It expands our ideas on what oceans can be," said Bill McKinnon, a Washington University professor and co-principal investigator of the New Horizons Mission. "We'll probably find, ultimately in our exploration, that things are even stranger than we think."

The ocean is likely located within the left ventricle of Pluto's large heart-shaped feature, Sputnik Planitia, a basin covered with nitrogen ice. McKinnon said that this part of Sputnik Planitia is aligned perfectly with Pluto's tidal axis, meaning that it's located at a point where the gravitational pull from the planet's largest moon Charon is the strongest. Pluto and Charon are tidally locked.

McKinnon remarked that Sputnik Planitia, which was likely formed by an ancient impact, is a truly unique feature in the solar system.

"All of Pluto's geology and climate evolution is controlled by this one feature," McKinnon said. "You can find big impacts [in the solar system]. And you can find where ice is condensed. But there's nothing quite like this."

While it might be difficult to imagine that something could survive in a sea of ammonia, McKinnon believes that nothing should be ruled out.

"We don't know of any kind of life that can live in such a situation, but it doesn't mean that people can't think about life that is not as we know it," McKinnon said.

The next stop for the New Horizons spacecraft is a Kuiper Belt object called 2014 MU69, which it's expected to reach by early 2019.

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